Accession Number : ADA136897

Title :   Investigation of Effects Contributing to Dynamic Stall Using a Momentum-Integral Method.

Descriptive Note : Master's thesis,

Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING

Personal Author(s) : Lawrence,J S

PDF Url : ADA136897

Report Date : Dec 1983

Pagination or Media Count : 108

Abstract : Dynamic stall effects are analyzed in this investigation for cases of an inertially static airfoil in a flow field rotating at constant rate (gust response), and an airfoil pitching at constant rate in a steady flow field. The method used is a boundary layer solution of the momentum-integral equation by a modified von Karman-Pohlhausen technique. Previous work using this method to match Kramer's experimental results for gust response is reviewed, corrected, and continued. The validity of the closure equation and the assumptions key to its derivation are examined, concluding that the closure equation is justified. A better match of Kramer's airfoil sections results in dynamic stall predictions very close to experimental data. The effect of varying airfoil thickness and camber is investigated. By consideration of the non-Newtonian motion of the boundary layer on the surface of a pitching airfoil, the momentum-integral method is extended to the second case. Using the Moore-Rott-Sears model for flow separation criteria, analytical results were computed and compared with experimental data. Reduction in adversity of the pressure gradient accounts for only a fraction of the total dynamic effect, and it is proposed that mass introduction into the boundary layer from the free stream may be a strongly contributing factor. This phenomena is demonstrated to have a large effect, and an argument is presented for the proper amount of mass introduction.

Descriptors :   *Flow separation, *Airfoils, *Angle of attack, *Integral equations, *Angular momentum, Boundary layer flow, Gusts, Pitch(Motion), Closures, Camber, Statics, Steady flow, Unsteady flow, Pressure gradients, Nonnewtonian fluids, Theses

Subject Categories : Aircraft
      Numerical Mathematics
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE